Is that something like a reduction? Of orange juice for example?

http://image.shutterstock.com/display_pic_with_logo/53554/53554,1171916802,2/stock-photo-starter-or-entree-of-a-french-dish-with-seafood-mixed-among-salad-leaves-2717460.jpg

Your guess is as good as mine! It could be a reduction or a puree of anything that is orange, edible and goes with the flavors of the dish. Cheers!

Do you know any websites to get some ideas of these? You know, what fruits or ingredients to use etc!

You can always try googling "plate decorating" or "plate design". There are also many book available either at the book store or maybe even your local library. Cheers!

Bobby Flay uses chile oil a lot for plating, and that looks a lot like it. Go to the Food Network website and search for it there, there's a couple of recipes for it. The 'Mesa Grill Cookbook' by Bobby Flay also has recipes for it.

There is also a recipe on Rouxbe for Roasted Tomato Oil, which is also a very bright orange color. Just not sure if the one in the picture is a color oil or not as it seems thicker. The photo also seems to be a very "food-styled" plate so who knows what they really used to achieve those orange dots.